Folate depletion occurs in the elderly despite adequate dietary intake. This suggests that intestinal folate malabsorption might be responsible. Furthermore, increased numbers of drugs have been shown to impede folate absorption. The aims of the proposed study are to measure simultaneously in free-living, disease-free elderly subjects, intestinal absorption of 14C labelled pteroyl-polyglutamte (14C PG-7) and 3H labelled pteroly-monoglutamate using a constant controlled jejunal perfusion system. The two forms of folate will be perfused at identical rates, the hydrolytic products of 14C PG-7 will be quantified and the absorption rate of both 3H and 14C folates measured by calculation of intestinal clearance and urinary appearance rates following perfusion. Simultaneously, net sodium and water flux from the test jejunal segment will be measured. The results will be compared to data on young healthy subjects perfused with identical solutions and under identical conditions. From the results of the proposed study, we will determine whether intestinal folate absorption is impaired in aging and whether any impairment is due to intestinal conjugase deficiency as suggested in the literature. The results will clarify whether dietary advice in some elderly subjects should include administration of synthetic folic acid. In addition, this pilot study will provide data as to whether intestinal perfusion studies of this nature are readily tolerated by elderly volunteers which would facilitate future physiologic and pathophysiologic studies of intestinal absorptive defects in aging.